This invention relates to improving a process for thermal cracking of retort oil in an elongated reactor.
This process is for thermal cracking of the gases and oil vapors produced by retorting oil shale, coal or tar sands. The term retorting denotes thermal conversion of the organic materials in these normally solid hydrocarbonaceous materials at temperatures in excess of 600.degree. F. (315.degree. C.). Retorting produces a retort effluent containing oil vapors, gases, and solid residues. The retort effluent is cooled to separate the gases from the oil. In some processes where the retort vapors contain an excessive amount of matrix solids, the retort effluent is passed through one or more quenchers and strippers to remove a substantial portion of the solids in the oil. Various ways of processing the retort oil have been proposed. The retort oil is usually processed to make a suitable oil for pipelining to the consumer. For example, the oil may be prerefined to a turbine fuel oil. In U.S. Pat. No. 4,080,285, it has been proposed to thermally crack shale oil in an elongated reactor without removing solids from the retort oil. Thermal cracking converts a portion of the retort oil directly into chemical feedstocks like ethylene, propylene, and butenes. This sort of thermal cracking of the retort oil has certain advantages, but the proposed cracking processes involve retort oil that has been separated from the retort gases and that has been cooled. The retort oil is usually reheated in a preheater prior to injecting the oil into the elongated reactor. Heating the retort oil creates coking problems in the heater thereby affecting the yield and product distributions of the cracking process.